Flow Simulations for Curb Opening Inlets with Different Longitudinal and Cross Slopes

Proper highway drainage is essential to ensure safe and comfortable conditions for the road users. The highway pavement and inlet geometry, especially cross slope and longitudinal slope and local depression and transition length, usually determine the highway surface drainage capacity. In this study, FLOW-3D is utilized to model the unsteady free-surface flow through curb opening inlets with different longitudinal and cross slopes. FLOW-3D, developed by the Flow Science, Inc., is a three-dimensional computational fluid dynamics software that can be utilized as "Virtual Lab" to study complex flow problems. FLOW-3D utilizes a true volume of fluid method (TruVOF) to compute free surface motion and the fractional area/volume obstacle representation (FAVOR) technique to model complex geometric regions. Flow characteristics near curb opening inlets are carefully examined. Inlet efficiency is determined from flow simulation results for the inlets with various longitudinal and cross slopes, especially for small slopes where laboratory tests were not able to be conducted. Inlet efficiencies for curb opening inlets with different transitional lengths before and after the inlet are examined using FLOW-3D simulation models. Simulation results are compared with laboratory observations with good agreement.